Overall objectives in proposed work: 1. To devlop an intact animal model using operant techniques to provide an index of extent of narcosis over a continuum of subanesthetic concentrations. 2. To determine dose-response relationships for representative inhalation and intravenous agents. 3. To utilize the information obtained from (1) and (2) to study the phenomena of parallelism and additivity among these various agents. 4. To study effects of repeated anesthetic exposure in terms of tolerance. Goals for the coming year: To develop specific dose-response curves for halothane and enflurane, singly and in combination, using the multiple FR-30 Fl-5 min. schedule.